In fight against Ebola, U.S. troops up against math. "The American military effort against history's deadliest Ebola outbreak is taking shape in West Africa, but concerns are mounting that the pace isn't fast enough to check a virus that is spreading at a terrifying clip....They will level swampy grassland, unload supplies and build tents, then train thousands of nurses from Sierra Leone and Liberia to treat Ebola. The epidemic in Liberia and Sierra Leone will likely worsen until 70% of Ebola patients can find room in a treatment center or other setting where they can't transmit the disease to others, the CDC said. Currently, just 18% do so, it said." Drew Hinshaw and Betsy McKay in The Wall Street Journal.

What's behind that magic 70 percent number? "Seventy percent is a number full of hope and dread....Right now, only about 18 percent of Ebola patients in Liberia are being isolated. Each day the epidemic persists makes 70 percent more difficult to reach....For every 30-day delay, the peak number of new daily cases triples, according to a model of the disease created by the CDC....Despite its reputation as a killer, Ebola isn’t very good at reproducing itself. The virus is spread through body fluids, not air, and it often kills patients before they have a chance to spread the disease widely. When 70 percent of patients are isolated, the disease no longer spreads fast enough to replace dying or recovering patients. It burns itself out." Tom Randall in Bloomberg.

Another barrier: Denial. "When stories circulate about a seemingly irrational response to disease, it's easy to dismiss the reaction as a bizarre denial of reality. But is it so hard to understand? In fact, attributing Ebola deaths to a curse is not as unreasonable as it might first seem....And we all are susceptible....Here in the United States, some parents opt against vaccinating their children....Some of the reaction in Ebola-affected areas is immediately understandable when put in context. Avoiding health facilities is reasonable if those facilities are associated with isolation and death, not cures....It's also important to consider the region's political history. In the past decade or so, both Liberia and Sierra Leone have emerged from debilitating civil wars." Hannah Bloch in NPR

WHO sees small-scale use of Ebola vaccine in January. "The World Health Organisation (WHO) said on Friday it expected to begin small-scale use of two experimental Ebola vaccines in West Africa early next year and in the meantime transfusions of survivors' blood may offer the best hope of treatment. WHO is working with pharmaceutical companies and regulators to accelerate the use of a range of potential treatments to fight the disease, a senior WHO official said." Stephanie Nebehay in Reuters.